1. Field of the Invention
The present invention relates to the field of recording and/or reproducing audio and video data on a digital recording medium, and more particularly, to a recording medium for storing audio data encrypted to prevent illegal copying, an apparatus for and a method of recording the same, and an apparatus for and a method of reproducing the same.
2. Description of the Related Art
An example of a digital recording medium for recording digital video and/or audio information is a digital versatile disc (DVD). Specifications for recording audio information on a DVD include, for example, a DVD specification for Read-Only Disc, Part 3, Video Specifications, Version 1.0, August 1995 (the DVD-Video Specification), and a DVD Specification for Read-Only Disc, Part 4, Audio Specifications, Version 1.0, March 1999, (the DVD-Audio Specification).
According to these specifications, high-quality video and audio information can be recorded on a disc. However, due to the characteristics of digital information, making a copy which reproduces sound almost the same as the original sound and picture is possible, and therefore a means to prevent illegal copying is needed.
A method which is widely used recently as a method for preventing illegal copying is to encrypt the recorded information. In the encryption method, all information or the most important part to be used in interpreting the information is encrypted so that copies cannot be used where the information is illegally copied.
However, the DVD-Video recording and/or reproducing apparatus and the DVD-Audio recording and/or reproducing apparatus define respective encryption methods for preventing illegal copying.
Since the DVD-Audio specification does not include provisions for moving pictures, in case of a music video, for which moving pictures and music are recorded together, moving picture information and music information are first made according to the DVD-Video specifications and recorded in a video region. Then, reproducing information for reproducing moving picture information and reproducing information for reproducing music information are recorded in a DVD-Video region and a DVD- Audio region, respectively, so that a DVD-Audio apparatus can reproduce both moving picture information and music information.
Meanwhile, since the DVD-Video specification is defined from the viewpoint that moving pictures are main and sound is auxiliary, the encryption method is applied only to video information and not applied to audio information. According to this, the decoding speed of the decoder can be raised, but prevention of illegal copying of audio information is difficult, which is contained in the music video and is very worthy of protection. Also, in case where audio information is encrypted according to a specification other than the existing DVD-Video specification, the audio information cannot be reproduced through the existing DVD-Video reproducing apparatus.
FIG. 1 illustrates the data structure on a DVD-ROM disc complying with the existing DVD-Video and DVD-Audio specifications, and explains the existing method for encrypting video information and audio information.
On the DVD-Video region on the DVD-ROM disc, video information 21, which can be protected from illegal copying through encryption, and audio information 22, which is not encrypted, are recorded. Also, reproducing management information (not shown) for reproducing the information is recorded.
On the DVD-Audio region of the DVD-ROM disc, audio information 23, which can be protected from illegal copying through an encryption method different from that of the video information, is recorded. Also in the DVD-Audio region, reproducing management information (not shown) for reproducing audio information 23, reproducing management information (not shown) for reproducing video information 21 and audio information 22 recorded in the DVD-Video region, and/or reproducing management information (not shown) for reproducing only audio information 22 recorded in the DVD-Video region are recorded.
Meanwhile, the DVD-Video specification defines provisions for encrypting only video information and does not provide an encryption method for encrypting audio information. That is, according to the DVD-Video specification, in case of music video in which audio information is main and moving picture information is auxiliary, encryption of the audio information, which is very worthy of protection, is impossible.
Also, the DVD-Audio specification does not stipulate a method or standard for recording moving picture information in a DVD-Audio region. Therefore, in the DVD-Audio specification, moving picture information cannot be recorded in the DVD-Audio region, and only reproducing management information for reproducing moving picture information recorded in the DVD-Video region, is recorded in the DVD-Audio region.
That is, only with the existing DVD-Audio specification and DVD-Video specification, a recording medium having a desired means for preventing illegal copying cannot be provided. Also, in a reproducing apparatus, which is made to reproduce DVD-Video information generated according to the existing DVD-Video specification, audio information recorded after being encrypted in a predetermined encryption method cannot be reproduced together with video information.